A.De Santis Radiative Meeting 30/05/07

Cross section ee

Antonio De Santis

Simona Giovannella

A.De Santis - Radiative Meeting 30/05/07 2 of 18

Amplitude

contribution in cross section (b) could be represented as interference with continuum process (a)Interference is parametrized by term (Z) at -resonace peak.

A.De Santis - Radiative Meeting 30/05/07 3 of 18

Data sample

Integrated luminosity onpeak 450 pb-1

Integrated luminosity offpeak 150 pb-1

Data:• drc (DBV-13/14) 01/02

• drc (DBV-24/25) 06

MC sample:• Signal (DBV-26 LSF=1) 01/02 (?)• mrc (DBV-18 all_phys LSF=0.2) 01/02• mrc (DVB-26 all_phys LSF=1(2)) 06

Total Luminosity: 600 pb-1

Scan 01/02

Scan 06

A.De Santis - Radiative Meeting 30/05/07 4 of 18

Analisys strategy

• Acceptance– One vertex at Interaction Point (IP)– Two tracks connected at vertex– Four neutral cluster with:

• Eclu grater than 10 MeV

• ToF compatible with prompt • |cos()| < 0.93

• Kinematic Fit (33 input parameters, 8 constraints) (?)

• Fine selection:– 2 < 50

– m/m

• Slice dataset in function of ECM (100 Kev Bin)

• Signal events counting (fit via HMCMLL) • Cross section fit

A.De Santis - Radiative Meeting 30/05/07 5 of 18

Data vs MC: cos()

2<50 2>50

MC fit

MC sig

Data

Same scale factors are used to normalize MC distributions in both selections

A.De Santis - Radiative Meeting 30/05/07 6 of 18

Data vs MC

2<50 2>50

MC fit

MC sig

Data

Same scale factors are used to normalize MC distributions in both selections

A.De Santis - Radiative Meeting 30/05/07 7 of 18

Data vs MC

2<50 2>50

MC fit

MC sig

Data

Same scale factors are used to normalize MC distributions in both selections

A.De Santis - Radiative Meeting 30/05/07 8 of 18

Data vs MC

2<50 2>50

MC fit

MC sig

Data

Same scale factors are used to normalize MC distributions in both selections

A.De Santis - Radiative Meeting 30/05/07 9 of 18

Data vs MC

2<50 2>50

MC fit

MC sig

Data

Same scale factors are used to normalize MC distributions in both selections

A.De Santis - Radiative Meeting 30/05/07 10 of 18

Data vs MC

ECoM =

1000 MeV

ECoM =

1010 MeV

ECoM =

1030 MeV

MC fit

MC sig

Data

A.De Santis - Radiative Meeting 30/05/07 11 of 18

Efficiency

Conditional efficiency:

tot = 40.07±0.03

A.De Santis - Radiative Meeting 30/05/07 12 of 18

Systematic errors I

Different source of systematic errorsare taken into account.

All of them are summed in quadraturewith statistic error of the counting fit toget the final error on the visible cross section

A.De Santis - Radiative Meeting 30/05/07 13 of 18

Cross section fit

tot

count

L

N

intexp

A.De Santis - Radiative Meeting 30/05/07 14 of 18

Fit result

A.De Santis - Radiative Meeting 30/05/07 15 of 18

Systematic errors II

Systematic errors on the fit parameters are evaluated as r.m.s. of the distributions obtained varying cuts and fitted distribution (counting).

Cross section stability as been checked for each CoM energy.

A.De Santis - Radiative Meeting 30/05/07 16 of 18

Final results

KLOE results:

SND results:

A.De Santis - Radiative Meeting 30/05/07 17 of 18

GoodNews

Referees at work

A.De Santis - Radiative Meeting 30/05/07 18 of 18

Conclusions

Cross section parameters accuracy better than SND results.

Agreement between results due to large errors in SND measurements.

Yesterday was my birthday and Today is exactly one months after my wedding and this work is completed…

…Life is Beautiful

A.De Santis - Radiative Meeting 30/05/07 19 of 18

Spare

A.De Santis - Radiative Meeting 30/05/07 20 of 18

Amplitude: MC generatorAll term which differs for exchange between two 0’s or different charge must be summed. Resulting matrix element (M) could be expressed as modulus squared of current composed by two term(0’s permutation) each composed by tree terms ( charge) 2002

0M

J

)(),,,(),,,(),,,( 3241323412314200

0 pppppptpppptpppptGJ

)()()()(

)()(

)(),,,(

31441324133142214334

431

12

4321

ppppppppppppppp

ppDpPD

pPFppppt

Reference: hep-ex/9904024 v2

A.De Santis - Radiative Meeting 30/05/07 21 of 18

Amplitude current term

Form factor

Inverse propagator

)()(

)()(

)()(

)(),,,(

3144132

4133142214334

431

12

4321

pppppp

ppppppppp

ppDpPD

pPFppppt

A.De Santis - Radiative Meeting 30/05/07 22 of 18

Major change in GEANFI

A.De Santis - Radiative Meeting 30/05/07 23 of 18

Kinematic fit

Input parameters:

0pppPγ γππφ

Constraints:

A.De Santis - Radiative Meeting 30/05/07 24 of 18

Measured visible cross section

tot

count

L

N

intexp

A.De Santis - Radiative Meeting 30/05/07 25 of 18

Tracking efficiency

A.De Santis - Radiative Meeting 30/05/07 26 of 18

Vertex efficiency

A.De Santis - Radiative Meeting 30/05/07 27 of 18

Eta filter and Bhabha filter